More questions. More specific now.

My house is bigger than the average house. I'll need a bigger stove, maybe. I have room to put in a lot more thermal mass. But it sounds like the typical rocket mass heater is already using just about all of the available heat. So I would need either a bigger fire to support the bigger thermal mass, or I would have to run it longer. I'd rather not baby sit it.


I have 5 cords of wood out there that I was going to burn in my normal woodstove. If I build a rocket mass stove I could burn it in that instead. Except the wood is all split to normal size. 1 stick would fit in a feed tube. It seems important to get the wood split down small not because of the feed tube size but rather to make it burn properly. *I am guessing* that the reason is that if the wood is not split down small enough it will not be as dry. If the wood is not as dry it will not burn hot enough to get a secondary burn going and the efficiency is lost. Even with the batch feeders it seems like the wood has to be split down smaller. I am wondering if more insulation and a longer burn tube would jack up the temperatures inside the tube causing a secondary burn even if the original temperatures are not as high. We have 10 food ceilings and a concrete floor, I have a lot of options. I wouldn't mind spending more money to create a stove that takes normal firewood but burns with rocket stove efficiency.


At this point one idea I have (it's just an idea at this point) is to take a normal wood stove and insulate/cover it with cob as much as possible to turn all of the heat back in on itself. Plug that into a long heavily insulated burn tube. Plug that into a long heavily insulated heat riser. The idea is that it would take longer to get warmed up and going, but it might burn bigger pieces of wood with the same efficiency since the added insulation would focus the heat more. So it would take less heat to cause the secondary burn, in theory.

I have a tractor and the ground is all good clay. So I can make whatever I want really.

Thoughts?

Short answer: go search "masonry stove" "masonry heater" "Russian stove" and "Russian heater".


Long answer: The need for small splits isn't about moisture content, but about air contact. If you've got just one fat piece of wood in your feed hole, then the air can only touch the outside surface, and the wood can only burn on the outside surface. If you split the same piece into four pieces, then think about how much more surface area it has.

I've also wished for a way to extract more heat out of a wood stove already in place. I don't think there's a good way. (Although, I did see a fella who made a "masonry hat.") The high temperatures that you're trying to achieve are right around the melting point of steel . Even if you fell well short of your target, you'll still be accelerating the corrosion and deterioration of the wood stove. (In addition, I suspect that the expansion and contraction of steel vs. the cob would promptly crack the arrangement apart, although I haven't seen this happen in real life.) If you have an abundance of clay, you might consider making old fashioned adobes and building a masonry stove. The firebox will need to be refractory, and can be any style you prefer, including a batch rocket. That, at least, is my own plan for next summer. Best of luck!

Frank G. : A suggestion; google '' High Temperature Hydrogen Attack '' to understand why you can not just add cob or insulation to the outside of a iron box type
Wood Stove !

Adding additional High Temp Firebrick to the inside of one of these wood stoves quickly chokes down the interior area to the point that you are right back at a too
small Combustion zone and you will be spending too much time feeding your Franken-Stove in order to get any amount of space heating !

Hope this helps and is timely ! Big AL !

I seem to remember Walter Jeffries on this forum posting about adapting a standard woodstove by adding thermal mass around it. www.sugarmtnfarm.com He has a blog where he describes the build. His family uses 3/4 cord to heat the house (Small and very well insulated).

Also Erica Wisener posted a link about the "ceramic hat" in the past. Mounted on top of the stove it was beautiful, if not a bit precarious. (built by Kiko Denzer (sp)?

As Al mentioned, don't have added mass in contact with the steel walls of the firebox. It will also cool the burn making it inefficent.

Mike Cantrell wrote:Short answer: go search "masonry stove" "masonry heater" "Russian stove" and "Russian heater".


Long answer: The need for small splits isn't about moisture content, but about air contact. If you've got just one fat piece of wood in your feed hole, then the air can only touch the outside surface, and the wood can only burn on the outside surface. If you split the same piece into four pieces, then think about how much more surface area it has.

Huh, I had that part wrong. It's a good thing I asked. Thanks for the info, it's a very important difference.

allen lumley wrote:Frank G. : A suggestion; google '' High Temperature Hydrogen Attack '' to understand why you can not just add cob or insulation to the outside of a iron box type
Wood Stove !

Adding additional High Temp Firebrick to the inside of one of these wood stoves quickly chokes down the interior area to the point that you are right back at a too
small Combustion zone and you will be spending too much time feeding your Franken-Stove in order to get any amount of space heating !

Hope this helps and is timely ! Big AL !

Dang. That looks like a bad thing to do to a piece of metal. Oh well. Better for me to learn this way instead of building one and having it break all up. Thanks.

Ok, I think I am getting closer. This guy build this stove. The firebox is bigger and cob insulated. He is burning multiple pieces of bigger wood. But the heat from those pieces is being choked down to a smaller flame path and focused, in what lookes to be a standard size rocket mass heater. He is controlling how much heat is being funneled down into the heater by controling how much air goes into the big firebox. The wood he is burning is the same size of what I burn in my wood stove.

It looks like there is more ash up front than in a normal rocket mass stove. I'll bet that is because of the logs being burned in a box with slower relative air flow and less heat. And I guess that is similar to the hybrid we have already seen. So, it is a trade off. Probably a trade off I can live with in order to avoid splitting wood down 5 times as small.

Let me know what you guys think about all of this.


Here is his video.

https://www.youtube.com/watch?v=Q2sFParAFEc

Frank G. : This is a horizontal bach-load type of Rocket Mass Heater, and is nearly as efficient as most j-Tube vertical load RMHs, as such they are a little outside
of my expertise! as such i would recommend at least trying to build a Regular J-tube type RMH before trying to advance beyond it to the slightly more complicated
horizontal feed RMH, After all, our goal here is to create the biggest group of supporters of the use of Rocket Mass Heaters RMHs as possible !

Several of the Forum members here are well experienced with th batch loading type of rocket Mass Heater and i am sure they will respond ! Hope this helps,
and is timely ! Big AL